The record rainfall and storm surges that have brought flooding across the UK are a clear sign that we are already experiencing the impacts of climate change.
Many
commentators have suggested that we are suffering from unprecedented
extreme weather. There are powerful grounds for arguing that this is
part of a trend.
Four of the five wettest years recorded in the UK
have occurred from the year 2000 onwards.
Over that same period, we
have also had the seven warmest years.
That is not a coincidence.
There is an increasing body of evidence that extreme daily rainfall
rates are becoming more intense, in line with what is expected from
fundamental physics, as the Met Office pointed out earlier this week.
A
warmer atmosphere holds more water.
Add to this the increase in sea
level, particularly along the English Channel, which is making storm
surges bigger, and it is clear why the risk of flooding in the UK is
rising.

Infra-red satellite animation from EUMETSAT showing a series of storms which have affected the United Kingdom and Ireland over the past two weeks.

But it is not just here that the impacts of climate change
have been felt through extreme weather events over the past few months.
Australia has just had its hottest year on record, during which it
suffered record-breaking heatwaves and severe bushfires in many parts of
the country.
And there has been more extreme heat over the past few
weeks.
Argentina had one of its worst heatwaves in late December,
while parts of Brazil were struck by floods and landslides following
record rainfall.

A ship washed ashore by typhoon Haiyan at Anibong in Tacloban,
Philippines, 5 February 2014. Photograph: Mark Tran for The Guardian

And very warm surface waters in the north-west Pacific during
November fuelled Typhoon Haiyan, the strongest tropical cyclone to make
landfall anywhere in the world, which killed more than 5,700 people in
the Philippines.

This is a pattern of global change that it would be very unwise to ignore.
The Intergovernmental Panel on Climate Change
last September pointed to a changing pattern of extreme weather since
1950, with more heatwaves and downpours in many parts of the world, as
the Earth has warmed by about 0.7C.
The IPCC has concluded from
all of the available scientific evidence that it is 95% likely that most
of the rise in global average temperature since the middle of the 20th
century is due to emissions of greenhouse gases, deforestation and other
human activities.

The upward trend in temperature is undeniable, despite the effects of
natural variability in the climate which causes the rate of warming to
temporarily accelerate or slow for short periods, as we have seen over
the past 15 years.
If we do not cut emissions, we face even more
devastating consequences, as unchecked they could raise global average
temperature to 4C or more above pre-industrial levels by the end of the
century.
This would be far above the threshold warming of 2C that
countries have already agreed that it would be dangerous to breach.
The
average temperature has not been 2C above pre-industrial levels for
about 115,000 years, when the ice-caps were smaller and global sea level
was at least five metres higher than today.
The shift to such a
world could cause mass migrations of hundreds of millions of people away
from the worst-affected areas.
That would lead to conflict and war, not
peace and prosperity.

Satellite photos of the river Parrett on the Somerset Levelstaken
before the recent flooding and on 8 February.

We also underestimated the potential
importance of strong feedbacks, such as the thawing of the permafrost
to release methane, a powerful greenhouse gas, as well as tipping points
beyond which some changes in the climate may become effectively
irreversible.
What we have experienced so far is surely small
relative to what could happen in the future.
We should remember that the
last time global temperature was 5C different from today, the Earth was
gripped by an ice age.
So the risks are immense and can only be
sensibly managed by reducing greenhouse gas emissions, which will
require a new low-carbon industrial revolution.
History teaches us
how quickly industrial transformations can occur through waves of
technological development, such as the introduction of electricity,
based on innovation and discovery.
We are already seeing
low-carbon technologies being deployed across the world, but further
progress will require investment and facing up to the real prices of
energy, including the very damaging emissions from fossil fuels.

Christian Gander makes his way through floodwater as he leaves his
home on Waterworks Road in Worcester.

Photograph: Joe Giddens/PA

Unfortunately, the current pace of progress is not nearly rapid
enough, with many rich industrialised countries being slow to make the
transition to cleaner and more efficient forms of economic growth.
The
lack of vision and political will from the leaders of many developed
countries is not just harming their long-term competitiveness, but is
also endangering efforts to create international co-operation and reach a
new agreement that should be signed in Paris in December 2015.

Delay
is dangerous.
Inaction could be justified only if we could have great
confidence that the risks posed by climate change are small.
But that is
not what 200 years of climate science is telling us.
The risks are
huge.

Fortunately poorer countries, such as China, are showing
leadership and beginning to demonstrate to the world how to invest in
low-carbon growth.
The UK must continue to set an example to other
countries.
The 2008 Climate Change Act, which commits the UK to cut its
emissions by at least 80% by 2050, is regarded around the world as a
model for how politicians can create the kind of clear policy signal to
the private sector which could generate billions of pounds of
investment.
Weakening the Act would be a great mistake and would
undermine a strong commitment made by all of the main political parties.
Squabbling
and inconsistent messages from ministers, as well as uncertainty about
the policies of possible future governments, are already eroding the
confidence of businesses.
Government-induced policy risk has become a
serious deterrent to private investment.
Instead, the UK should
work with the rest of the European Union to create a unified and much
better functioning energy market and power grid structure.
This would
also increase energy security, lower costs and reduce emissions.
What
better way is there to bring Europe together?

The government will also have to ensure the country becomes more
resilient to those impacts of climate change that cannot now be avoided,
including by investing greater sums in flood defences.
It should
resist calls from some politicians and parts of media to fund adaptation
to climate change by cutting overseas aid.
It would be deeply immoral
to penalise the 1.2 billion people around the world who live in extreme
poverty.
In fact, the UK should be increasing aid to poor
countries to help them develop economically in a climate that is
becoming more hostile largely because of past emissions by rich
countries.
A much more sensible way to raise money would be to
implement a strong price on greenhouse gas pollution across the economy,
which would also help to reduce emissions.
It is essential that the
government seizes this opportunity to foster the wave of low-carbon
technological development and innovation that will drive economic growth
and avoid the enormous risks of unmanaged climate change.